Isolating the Contributions of Specific Network Sites to the Diffuse Vibrational Spectrum of Interfacial Water with Isotopomer-Selective Spectroscopy of Cold Clusters
Isolating the Contributions of Specific Network Sites to the Diffuse Vibrational Spectrum of Interfacial Water with Isotopomer-Selective Spectroscopy of Cold Clusters
复制标题
用冷团簇同位素选择性光谱法分离特定网络位点对界面水漫反射振动谱的贡献
DOI：
10.1021/acs.jpca.0c07795
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Xantheas, Sotiris S.
中科院分区：
文献类型：
--
作者：
Yang, Nan;Khuu, Thien;Mitra, Sayoni;Duong, Chinh H.;Johnson, Mark A.;DiRisio, Ryan J.;McCoy, Anne B.;Miliordos, Evangelos;Xantheas, Sotiris S.
解码水的界面振动光谱中包含的结构信息需要了解单个水分子的光谱特征如何响应其局部氢键环境。在这项研究中，我们分离出的贡献，根据不同的供体（D）和受体（A）的氢键，每个网站的数量不同的网站。这些模式是利用一系列阳离子M+·（H2O）n（M = Li，Na，Cs，NH 4，CH 3 NH3，H3 O，n = 5，20-22）水合时在气相中形成的水簇笼结构的独特性质来测量的。选择这种离子以系统地表达A、AD、AAD、ADD和AADD氢键基序。每个网站的光谱特征进行了测量，使用双色，红外-红外同位素选择性photodegradation振动光谱的低温冷却，质量选择的集群离子，其中一个单一的完整的H2O的引入没有同位素混乱，一个重要的优势，由集群制度。由此产生的图案提供了一个前所未有的图片的固有线的形状和光谱的复杂性与激发的个别OH基团，以及在同一个水分子上的两个OH基团的频率之间的相关性，作为网络站点的功能。周围的水网络，管理这个频率图的属性进行评估，通过解剖电子结构的计算，探讨如何在附近的网络结构的变化，无论是内部和外部的第一水化壳，影响OH振荡器的本地频率。的定性趋势恢复与一个简单的模型，该模型与OH键的中心的网络调制的局部电子密度的OH频率。
Decoding the structural information contained in the interfacial vibrational spectrum of water requires understanding how the spectral signatures of individual water molecules respond to their local hydrogen bonding environments. In this study, we isolated the contributions for the five classes of sites that differ according to the number of donor (D) and acceptor (A) hydrogen bonds that characterize each site. These patterns were measured by exploiting the unique properties of the water cluster cage structures formed in the gas phase upon hydration of a series of cations M+·(H2O)n(M = Li, Na, Cs, NH4, CH3NH3, H3O, andn= 5, 20–22). This selection of ions was chosen to systematically express the A, AD, AAD, ADD, and AADD hydrogen bonding motifs. The spectral signatures of each site were measured using two-color, IR–IR isotopomer-selective photofragmentation vibrational spectroscopy of the cryogenically cooled, mass selected cluster ions in which a single intact H2O is introduced without isotopic scrambling, an important advantage afforded by the cluster regime. The resulting patterns provide an unprecedented picture of the intrinsic line shapes and spectral complexities associated with excitation of the individual OH groups, as well as the correlation between the frequencies of the two OH groups on the same water molecule, as a function of network site. The properties of the surrounding water network that govern this frequency map are evaluated by dissecting electronic structure calculations that explore how changes in the nearby network structures, both within and beyond the first hydration shell, affect the local frequency of an OH oscillator. The qualitative trends are recovered with a simple model that correlates the OH frequency with the network-modulated local electron density in the center of the OH bond.